Settling apparatus



Jan. 3, R KLQPPER 3,295,835

SETTLING APPARATUS Filed May 11, 1965 4 Sheets-Sheet l INVENTOR DANIELR. KLOPPfER D. R. KLOPPER Jan. 3, 1967 SETTLING APPARATUS 4 Sheets-Sheet2 Filed May 11, 1965 INVENTOR DANREL KLOPPER Jan. 3, 1967 INVENTO RDANIEL R- KLOFPER 1967 D. R. KLOPPER SETTLING APPARATUS 4 Sheets-Sheet 4Filed May 11, 1965 N R KLo FPER 9M y aeys United States Patent 3,295,835SETTLING APPARATUS Daniel R. Klopper, Brendan, Transvaal, Republic ofSouth Africa, assignor to Union Corporation Limited, Transvaal, Republicof South Africa Filed May 11, 1965, Ser. No. 454,946 Claims priority,application Republic of South Africa, May 22, 1964, 64/2,420 12 Claims.(Cl. 259108) This invention relates to settling apparatus, such as forslime, slurries, sludges or the like, which are often referred to assettlers, thickeners or clarifiers.

It is well known to provide a thickener including a settling tank, androtary raking gear located in the tank and arranged to be rotatedthrough fluid in the tank about a vertical axis.

Hitherto, the raking gear has been of substantial constructionpresenting large settlement areas for pulp, as well as large projectedareas in the direction of travel which increase resistance to movementand cause disturbance of pulp in suspension. Pulp settlement increasesthe weight of moving parts and also the projected areas in the directionof movement, thereby increasing resistance to movement of the rakinggear through the fluid and the disturbance of pulp in suspension. Undercertain circumstances, pulp settlement can present serious problems.

Due to the considerable weight of the moving parts, it has hitherto beennecessary to provide substantial supporting structure. As can beexpected, the cost of conventional raking gear and supporting structuretherefor is considerable.

In order to avoid or at least to minimize damage in the event of theraking gear encountering obstacles during travel through the fluid, ithas been suggested to provide means sensitive to the load current drawnby a driving motor for the raking gear, for lifting the raking gear fromits normal operating position in the tank. This ar rangernent suifersfrom the disadvantage that there is a time lag between a rise in loadcurrent due to the movement of the raking gear through the fluid beingresisted, and the raking gear actually being lifted. In the result, itoften happens that the raking gear has either cleared the obstacle orhas been damaged by the time the lifting occurs. Also, the equipmentinvolved is relatively complicated and expensive.

In another arrangement, drive means for the raking gear is mounted oninclined surfaces, the arrangement being such that normally the drivemeans is stationary whilst it rotates the raking gear, but is itselfrotated against the inclination of the surfaces in opposite direction tothe raking gear to lift the latter, when the reaction of driving torqueexceeds a predetermined value. This arrangement is effective inminimizing damage for in the event of the resistance to movement of theraking gear becoming too high, the raking gear stops and the drive meansrides up the inclined surfaces in reverse direction under the influenceof the resultant reactional driving torque. However, relativelycomplicated and expensive equipment is required and eificiency isdecreased due to stoppage of the raking gear.

It is an object of the present invention to provide improved rakingmeans which is relatively cheap and simple in design, yet eifective inoperation.

According to the invention a thickener comprises a settling tank; androtary raking means including at least one raking blade carrier armlocated within the settling tank in required angular relationship to thehorizontal and mounted towards one end for rotation about asubstantially vertical axis and for pivotal movement at least about asubstantially horizontal axis; and at least one elongated draughtelement secured to the carrier arm, draught force acting along a closedpat-h about the vertical axis of rotation or the carrier arm beingapplicable to the draught element in a position above and in advance ofthe carrier arm..

A plurality of draught elements may be secured to the carrier arm inpositions spaced along the length of the arm, the elements convergingupwardly and forwardly from the carrier arm to a common centre zone inthe proximity of which draught force is applicable to the elements.

Preferably, a pair of carrier arms extend radially in oppositedirections from a common substantially vertical axis of rotation and aremounted towards their inner ends for rotation together about the commonvertical axis, each carrier arm further being mounted towards its innerend for individual pivotal movement independently of the other carrierarm about a substantially horizontal axis as well as about asubstantially vertical axis.

The raking means may further include a drive arm for the or each carrierarm, each drive arm being located above and in advance of its carrierarm and arranged to be rotationally driven substantially about thevertical axis of rotation of the associated carrier arm, the draughtelement or elements of the associated carrier arm being secured to thedrive arm.

A'plurality of draught elements of the or each carrier arm may besecured to the associated drive arm in a conmon centre zone spaced fromthe vertical rotational axis of the drive arm.

Raking blades of any suitable design may be mounted in any suitablearrangement along the length of the or each carrier arm.

The or each carrier arm is preferably in the form of a plain tubularmember presenting a minimum settlement area for pulp and a minimumprojected area in the direction of travel. The weight of the carrierarms can thus be reduced to a minimum.

The or each draught element may be secured to the associated carrier armin such a manner that the action of draught force on the carrier armcounteracts twisting moments on the carrier arm set up by loading of theraking blades.

Thus, there may be provided for the or each draught element on itsassociated carrier arm, an anchor bracket fast with and extendingtransversely from the oarrier arm, the draught element being secured tothe anchor bracket in a position spaced from the carrier arm and theanchor bracket extending in a direction whereby twisting moment on thecarrier arm due to draught force on the draught element acts in oppositedirection to twisting moment on the carrier arm due to loading of rakingblades on the carrier arm during operation.

The invention includes within its scope thickener raking means asdefined above.

A preferred embodiment of the invention willnow be described by way ofexample with reference to the accompanying drawings in which:

FIGURE 1 is a sectional elevation of a thickener incorporating rakingmeans according to the invention.

FIGURE 2 is a plan of the thickener of FIGURE 1 with parts broken awayto show the raking means clearly.

FIGURE 3 is a fragmentary perspective view to an enlarged scale of thecentralbottom zone of the settling tank of FIGURES 1 and 2, showing thebottom mounting anchoring draught elements to the drive arm.

FIGURE is a perspective view to an enlarged scale of portion of acarrier arm of the raking means of FIGURES 1 and 2, showing the mountingof raking blades on the carrier arm.

FIGURE 6 is a perspective view to an enlarged scale of portion of acarrier arm of the raking means of FIGURES 1 and 2, showing a bracketfor anchoring a draught element to the carrier arm.

FIGURE 7 is a perspective view of the anchor bracket of FIGURE 6.

FIGURE 8 is an elevational view of the carrier arm portion and anchorbracket of FIGURE 6.

Referring to FIGURES 1, 2 and 3, the thickener comprises settling tank 1having base 2 sloping downwardly and inwardly towards centrally locatedoutlet 3 communicating with discharge funnel 4. It will be seen thatbase 2 comprises two portions 2a and 2b having different inclinations.

Overhead gangway 5 traverses tank 1 and carries drive means 6 includingelectric motor 7 drivingly coupled to vertical drive shaft 8. Motor 7may be coupled to drive shaft 8 and drive shaft 8 may be rotatablysuspended from drive means 6 or from the mounting of drive means 6 inany suitable manner as will be clear to a man skilled in the art.

Overhead feed launder 9 extends radially inwards from the edge of tank 1and terminates in annular feed well 10.

A pair of horizontal drive arms 11 are fast with and extend radially inopposite directions away from drive shaft 8 which is arranged to berotatably driven about its own axis. Drive arms 11 and drive shaft 8 aremounted coaxially with settling tank 1 in a position just above thewater level A in tank 1.

Support shaft 12 is fast with and depends from drive arms 11 in co-axialrelationship to drive shaft 8. At its lower end support shaft 12 is fastwith co-axial locating shaft 13 held at its lower end in bearing 14mounted at the bottom of tank 1 above discharge funnel 4 by means ofradial arms 15 carried at their outer ends on support flange 4a ofdischarge funnel 4.

A pair of tubular carrier arms 16 are located within tank 1 below waterlevel A and extend radially in opposite directions away from supportshaft 12 at a suitable inclination relative to the horizontal inaccordance with the slope of base 2 of tank 1.

As shown in FIGURE 3, support flange 17 is fast with the lower end ofsupport shaft 12 and carries a pair of vertically disposed pivot members18 presenting threaded spigots 19 passing through vertically facingapertures in flange 17 to permit rotational movement of pivot members 18relative to flange 17 and support shaft 12 about the vertical axes ofspigots 19 which are spaced from the axis of support shaft 12. Pivotmembers 18 are held by nuts 20 on spigots 19.

At its inner end each carrier arm 16 presents a clevis 21 receiving thelower end of a pivot member 1 8. Each clevis 21 is mounted on its pivotmember 18 by means of a horizontal pin 22 for pivotal movement about thehorizontal axis of pin 22.

It will be appreciated that carrier arms 16 are mounted at their innerends on support shaft 12 for rotation therewith about its vertical axis.Additionally, each carrier arm 16 is mounted at its inner end forindividual pivotal movement independently of the other carrier arm abouta horizontal axis spaced from the vertical axis of drive shaft 8, aswell as about a vertical axis spaced from the vertical axis of driveshaft 8.

A series of raking blades 23 are mounted in any suitable arrangementalong the length of each carrier arm 16. As shown in FIGURE 5, eachblade 23 engages its carrier arm 16 with a notch 24 and is secured toits carrier arm by means of Welding 25.

A plurality of draught ropes 26 are anchored to each carrier arm 16 inspaced relationship along its length and converge upwardly and forwardlyto securing plate 27 located on the outer end of the associated drivearm 11 in a position spaced from the vertical axis of rotation of driveshaft 8. As shown clearly in FIGURE 4, securing plate 27 presents aseries of apertures 28 located on the circumference of a circle. Draughtropes 26 are secured each in its own aperture 28, such as by means of ashackle (not shown), so that ropes 26 diverge downwardly and rearwardlytowards their carrier arm 16 from a common centre.

Referring to FIGURES 6 to 8, it will be seen that each draught rope isanchored to its associated carrier arm 16 by means of an anchor bracket29 fast with the carrier arm 16 and extending transversely awaytherefrom. Plate 29a of each anchor bracket 29 leans forwardly an angle1 relative to the vertical and the associated draught rope 26 is securedto plate 29a in a position spaced from carrier arm 16. 1

Upon rotation of drive arms 11 with drive shaft 8 about the verticalaxis of the latter, draught force acting along a closed path 30 aboutthe vertical axis of drive shaft 8 is applied to each draught rope 26 ina position above and in advance of its associated carrier arm 16 so thatthe latter is dragged about the vertical axis of rotation of supportshaft 12 at a suitable angle 6 behind its drive arm 11. The pair ofcarrier arms 16 rotate together about the vertical axis of support shaft12.

Since support shaft 12 is fast with drive arms 11 and thereforerotatably coupled to drive shaft 8, a certain amount of driving torqueis likely to be transmitted to carrier arms 16 through their inner endmountings from support shaft 12. However, the inner end mountings are soclose to the rotational axis of support shaft 12 that this drivingtorque is negligible and substantially all the driving torque isobtained from drive arms 11 and draught ropes 26.

It will be seen from FIGURE 4 that portion 27a of securing plate 27which contains apertures 28, is bent downwardly at an angle 5 to thehorizontal so that the drag exerted on securing plate 27 by draughtropes 26 acts substantially in the plane of portion 27a. Also, as can beseen from FIGURE 8, each anchor bracket plate 29a leans sideways at anappropriate angle to the vertical and in an appropriate directiondepending on its position along carrier arm 16 so that draught forceapplied to the anchor bracket 29 acts substantially in the plane ofplate 2901.

By reading FIGURES 5 and 6 together, it will be seen that when carrierarm 16 moves forwardly in the direction of arrow B during operation ofthe thickener, a twisting moment acting anticlockwise in the directionof arrow C in FIGURE 5 is imposed on carrier arm 16 as a result ofloading of raking blades 23. Anchor brackets 29 extend from carrier arm16 in such direction that a twisting moment acting clockwise in thedirection of arrow D in FIGURE 6 is imposed on carrier arm 16 as aresult of draught force exerted on anchor brackets 29 by draught ropes26. Thus, the action of draught force on carrier arms 16 counteractstwisting moments on carrier arms 16 set up by loading of raking blades23.

In the event of the raking blades 23 of a carrier arm 16 encountering anobstacle during rotation about the vertical axis of support shaft 12,the tension in the associated draught ropes 26 increases and the carrierarm is automatically pivoted upwardly about the horizontal axis of itspivot pin 22 at its inner end. Draught ropes 26 are of fixed length andtheir lower ends will thus move along the circumference of circleslocated in generally vertical planes. Also, a carrier arm is capable ofpivoting rearwardly about the vertical axis of its pivot member 18.Thus,'upon being pivoted upwardly under the influence of an increase inresistance to rotational movement about the vertical axis of drive shaft8, a carrier arm 16 will lift in rearward direction to increase theangle of lag 6 of the carrier arm 16 behind its drive arm 11.

The effect of upward and rearward pivotal movement of a carrier arm 16about the horizontal and vertical axes at its inner end, is to lift theassociated raking blades 23 upwardly and rearwardly out of pulp in tank1, thereby to decrease drag on carrier arm 16. Load on driving means 6is therefore adjusted automatically. The load regulating action is fastacting and raking blades 23 can deal effectively with unevendistribution of pulp in tank 1.

In the event of a solid obstacle being encountered, raking blades 23 Ofeach carrier arm 16 passing the obstacle will be lifted over theobstacle and 'will act to scrape the upper surface thereof. Successivepassages of raking blades 23 will gradually wear away the obstaclewithout overloading the raking means.

-Upon upward pivotal movement of a carrier arm 16, lift of the scraperblades 23 towards the inner end of the carrier arm is a minimum, so thateffective sweeping in the central zone in the neighborhood of tankoutlet 3 is maintained to prevent clogging.

As shown in FIGURE 1, a suspension rope 31 for each carrier arm 16 isfast at one end with the associated overhead drive arm 11 in a positionadjacent the vertical axis of rotation of the latter, and fast at theother end with the carrier arm 16 in a suitable position intermediatethe ends of the latter. Suspension ropes 31 merely determine the lowestposition of carrier arms 16 to prevent them from scraping base 2 of tank1 during starting and stopping. It is believed that during normaloperation, tension on draught ropes 26 support carrier arms 16 inrequired disposition and that suspension ropes 31 are to all intents andpurposes inoperative. Suspension ropes 31 do not interfere with upwardand rearward pivotal movement of carrier arms 16.

With raking means according to the invention, the drive arms can bemounted entirely above the water level.

No driving torque for the blade carrier arms need be transmitted throughthe pivotal mounting at the inner ends of the blade carrier arms and canbe applied solely through the draught elements. This permits a reductionin the structural strength, physical dimensions and weight of the bladecarrier arms and their inner end mountings.

The physical dimensions of moving parts located below the water levelcan be kept down to a minimum in order:

(a) To present a minimum projected area in the direction of travelthereby to minimise disturbance of pulp in suspension and resistance tomovement, and

(b) to present a minimum settlement area for pulp in order to minimisebuild up of weight of moving parts, disturbance of pulp in suspensionand resistance to movement.

The weight of moving parts located below water level can be reduced,thereby permitting a reduction in the size and strength and consequentlythe cost of support structure therefor.

Raking means according to the invention is relatively cheap and simplein design, yet effective in operation.

It will be appreciated that many variations in detail are possiblewithout departing from the scope of the appended claims.

What I claim is:

1. A thickener comprising a settling tank; a vertical drive shaftlocated co-axially relative to the settling tank and arranged to berotatably driven; a pair of drive arms located in the region of theliquid level of the settling tank, the drive arms being fast with andextending radially in opposite directions from the drive shaft; asupport shaft fast with the drive arms and depending therefrom inco-axial relationship to the drive shaft; 3. plain tubular raking bladecarrier arm for each drive arm, located within the settling tank belowand rearwardly of the associated drive arm, the carrier arms extendingradially in opposite directions from the support shaft and being mountedtowards their inner ends on the support shaft for rotation with thesupport shaft about its vertical axis, each carrier arm further beingmounted towards its inner end on the support shaft for individualpivotal movement independently of the other carrier arm about asubstantially horizontal axis spaced from the vertical axis of thesupport shaft as well as about a substantially vertical axis spaced fromthe vertical axis of the support shaft; and a plurality of draughtelements for each carrier arm, each set of draught elements beingsecured to their carrier arm in positions spaced along the length of thecarrier arm and each set of elements converging upwardly and forwardlyfrom their carrier arm to a common centre zone spaced from the verticalrotational axis of the drive shaft and each set of elements beingsecured to the associated drive arm in their centre zone.

2. Settling apparatus comprising a settling tank; rotary raking meanscomprising at least a pair of raking blade carrier arms located withinthe settling tank in required angular relationship to the horizontal andextending radially in circumferential spaced relationship from a common,substantially vertical axis of rotation, the carrier arms being mountedtowards their inner ends for rotation together about the common verticalaxis and each carrier arm further being mounted towards its inner endfor individual pivotal movement independently of the other carrier armabout both a substantially horizontal axis and a substantially verticalaxis; and at least one elongated draught element secured to each carrierarm, whereby draught force acting along a closed path about the verticalaxis of rotation of the carrier arms is applicable to each draughtelement in a position above and in advance of its carrier arm.

3. Settling means as claimed in claim 2, wherein the carrier armscomprise plain tubular members, and a plurality of draught elements aresecured to each carrier arm in positions spaced along the length of thearm.

4. Settling means as claimed in claim 2, including a drive arm for eachcarrier arm, each drive arm being located above and in advance of itscarrier arm, and means for rotating each drive arm substantially aboutthe vertical axis of rotation of the carrier arms, the draught elementof each carrier arm being secured to the associated drive arm.

5. Settling apparatus comprising a settling tank; rotary raking meanscomprising at least a pair of plain, tubular raking blade carrier armslocated within the settling tank in required angular relationship to thehorizontal and extending radially in circumferential spaced relationshipfrom a common, substantially vertical axis of rotation, the carrier armsbeing mounted towards its inner end for individual pivotal movementindependently of the other carrier arm about both a substantiallyhorizontal axis and a substantially vertical axis; a drive arm for eachcarrier arm, each drive arm being located above and in advance of theassociated carrier arm and arranged to be rotationally drivensubstantially about the vertical axis of rotation of the associatedcarrier arm; and a plurality of draught elements secured to each carrierarm in positions spaced along the length of the arm, the draughtelements of each carrier arm converging upwardly and forwardly fromtheir carrier arm to a common center zone spaced from the verticalrotational axis of the associated drive arm and the draught elements ofeach carrier arm being secured to the associated drive arm in theircenter zone.

6. Settling apparatus comprising a settling tank; rotary raking meanscomprising at least a pair of raking blade carrier arms located withinthe settling tank in required angular relationship to the horizontal andextending radially in circumferential spaced relationship from a common,substantially vertical axis of rotation, the carrier arms being mountedtowards their inner ends for rotation together about the common verticalaxis and each carrier arm further being mounted towards its inner endfor individual pivotal movement independently of the other carrier armabout both a substantially horizontal axis and a substantially verticalaxis; at least one elongated draught element secured to each carrierarm, whereby draught force acting along a closed path about the verticalaxis of rotation of the carrier arms is applicable to each draughtelement in a position above and in advance of its carrier arm; and ananchor bracket fast with and extending transversely from each carrierarm, the draught element for each carrier arm being secured to the associated anchor bracket in a position spaced from the carrier arm and theanchor bracket extending in a direction whereby twisting moment on thecarrier due to draught force on the draught element acts in oppositedirection to twisting moment on the carrier arm due to loading of rakingblades on the carrier arm during operation.

7. Settling apparatus comprising a settling tank; rotary raking meanscomprising at least a pair of plain, tubular raking blade carrier armslocated within the settling tank in required angular relationship to thehorizontal and extending radially in circumferential spaced relationshipfrom a common, substantially vertical axis of rotation, the carrier armsbeing mounted towards their inner ends for rotation together about thecommon vertical axis and each carrier arm further being mounted towardsits inner end for individual pivotal movement independently of the othercarrier arm about both a substantially horizontal axis and asubstantially vertical axis; a drive arm for each carrier arm, eachdrive arm being located above and in advance of the associated carrierarm and arranged to be rotationally driven substantially about thevertical axis of rotation of the associated carrier arm; a plurality ofanchor brackets fast with each carrier arm in positions spaced along thelength of the carrier arm, each anchor bracket extending transverselyfrom its carrier arm; and an elongated draught element for and securedto each anchor bracket in a position spaced from the associated carrierarm, the draught elements of each carrier arm converging upwardly andforwardly from their carrier arm to a common center zone spaced from thevertical rotational axis of the associated drive arm and secured to theassociated drive arm in a direction whereby twisting moment on thecarrier arm due to draught force on the associated draught element actsin opposite direction to twisting moment on the carrier arm due toloading of raking blades on the carrier arm during operation.

8. Raking means for settling apparatus incorporating a settling tank,comprising at least a pair of raking blade carrier arms locatable withinthe settling tank in required angular relationship to the horizontal toextend radially in circumferential spaced relationship from a common,substantially vertical axis of rotation, the carrier arms beingmountable towards their inner ends for rotation together about thecommon vertical axis and each carrier arm further being mountabletowards its inner end for individual pivotal movement independently ofthe other carrier arm about both a substantially horizontal axis and asubstantially vertical axis.

9. Raking means as claimed in claim 8, wherein the carrier arms compriseplain tubular members, and a plurality of draught elements are securedto each carrier arm in positions spaced along the length of the arm,draught force acting along a closed path about the vertical axis ofrotation of the carrier arms being applicable to each draught element ina position above and in advance of its carrier arms.

10. Raking means for settling apparatus incorporating a settling tank,comprising at least a pair of raking blade carrier arms locatable withinthe settling tank in required angular relationship to the horizontal toextend radially in circumferential spaced relationship from a common,substantially vertical axis of rotation, the carrier arms beingmountable towards their inner ends for rotation together about thecommon vertical axis and each carrier arm further being mountabletowards its inner end for individual pivotal movement independently ofthe other carrier arm about a substantially horizontal axis as well asabout a substantially vertical axis; a drive arm for each carrier arm,each drive arm being located above and in advance of the associatedcarrier arm and arranged to be rotationally driven substantially aboutthe vertical axis of rotation of the associated carrier arm; and aplurality of draught elements secured to each carrier arm in positionsspaced along the length of the arm, the draught elements of each carrierarm converging upwardly and forwardly from their carrier arm to a commoncenter zone spaced from the vertical rotational axis of the associateddrive arm and the draught elements of each carrier arm being secured tothe associated drive arm in their center zone.

11. Raking means for settling apparatus incorporating a settling tank,comprising at least a pair of raking blade carrier arms locatable withinthe settling tank in required angular relationship to the horizontal toextend radially in circumferential spaced relationship from a common,substantially vertical axis of rotation, the carrier arms beingmountable towards their inner ends for rotation together about thecommon vertical axis and each carrier arm further being mountabletowards its inner end for individual pivotal movement independently ofthe other carrier arm about a substantially horizontal axis as well asabout a substantially vertical axis; a drive arm for each carrier arm,each drive arm being located above and in advance of the associatedcarrier arm and arranged to be rotationally driven substantially aboutthe vertical axis of rotation of the associated carrier arm; a pluralityof anchor brackets fast with each carrier arm in positions spaced alongthe length of the carrier arm, each anchor bracket extendingtransversely from its carrier arm; and an elongated draught element forand secured to each anchor bracket in a position spaced from theassociated carrier arm, the draught elements of each carrier armconverging upwardly and forwardly from their carrier arm to a commoncenter zone spaced from the vertical rotational axis of the associateddrive arm and secured to the associated drive arm in their center zone,each anchor bracket extending from its carrier arm in a directionwhereby twisting moment on the carrier arm due to draught force on theassociated draught element acts in opposite direction to twisting momenton the carrier arm due to unloading of raking blades on the carrierduring operation.

12. Raking means for settling apparatus incorporating a settling tank,comprising a raking blade carrier arm locatable within the settling tankin required angular relationship to the horizontal and mountable towardsone end for rotation about a substantially vertical axis and for pivotalmovement about a substantially horizontal axis as well as about asubstantially vertical axis; and at least one anchor bracket fast withand extending transversely from the carrier arm, a draught element beingsecurable to the anchor bracket in a position spaced from the carrierarm and the anchor bracket extending in a direction whereby twistingmoment on the carrier arm due to draught force on the draught elementacts in the opposite direction to twisting moment on the carrier arm dueto loading of raking blades on the carrier arm during operation.

References Cited by the Examiner UNITED STATES PATENTS 964,935 7/1910Baril 259 10s 2,322,720 6/1943 Scott et al 259 10s 2,557,316 6/1951Scott 210 531 3,166,502 1/1965 Kelly 210-528 FOREIGN PATENTS 583,27312/1946 Great Britain.

WALTER A. SCHEEL, Primary Examiner. Wt JENKINS, As istant Examinerr

2. SETTLING APPARATUS COMPRISING A SETTLING TANK; ROTARY RAKING MEANSCOMPRISING AT LEAST A PAIR OF RAKING BLADE CARRIER ARMS LOCATED WITHINTHE SETTLING TANK IN REQUIRED ANGULAR RELATIONSHIP TO THE HORIZONTAL ANDEXTENDING RADIALLY IN CIRCUMFERENTIAL SPACED RELATIONSHIP FROM A COMMON,SUBSTANTIALLY VERTICAL AXIS OF ROTATION, THE CARRIER ARMS BEING MOUNTEDTOWARDS THEIR INNER ENDS FOR ROTATION TOGETHER ABOUT THE COMMON VERTICALAXIS AND EACH CARRIER ARM FURTHER BEING MOUNTED TOWARDS ITS INNER ENDFOR INDIVIDUAL PIVOTAL MOVEMENT INDEPENDENTLY OF THE OTHER CARRIER ARMABOUT BOTH A SUBSTANTIALLY HORIZONTAL AXIS AND A SUBSTANTIALLY VERTICALAXIS; AND AT LEAST ONE ELONGATED DRAUGHT ELEMENT SECURED TO EACH CARRIERARM, WHEREBY DRAUGHT FORCE ACTING ALONG A CLOSED PATH ABOUT THE VERTICALAXIS OF ROTATION OF THE CARRIER ARMS IS APPLICABLE TO EACH DRAUGHTELEMENT IN A POSITION ABOVE AND IN ADVANCE OF ITS CARRIER ARM.